The present invention relates to a fuel cell vehicle equipped with a fuel cell system and a method for controlling the fuel cell vehicle.
Vehicles (for example, forklifts and other industrial vehicles) equipped with fuel cell systems have been in practical use. In the fuel cell system disclosed in Japanese Laid-Open Patent Publication No. 2014-82056, in-vehicle electric loads are connected to a fuel cell stack. Also, a capacitor, which serves as a power storage device, is connected to the fuel cell stack so as to be connected in parallel with the in-vehicle electric loads. When the generated power of the fuel cell stack exceeds the power required by the in-vehicle electric loads, the surplus power is used to charge the capacitor. In contrast, when the generated power falls below the power required by the in-vehicle electric loads, the capacitor discharges the power corresponding to the insufficiency.
For example, when the vehicle goes up a steep hill with a heavy cargo, the power that the fuel cell system is required to generate exceeds the rating of the fuel cell system, so that the power of the capacitor is used. If such a situation continues for a long time or frequently occurs, the state of charge (SOC) of the capacitor decreases, leading to a possibility of overdischarge of the capacitor. In order to prevent the capacitor from overdischarging and to protect the capacitor, it is necessary to stop the fuel cell system and shut down the other systems of the vehicle in an emergency.
However, such a system shut-down would hinder operations where the vehicle is used and thus should be avoided as much as possible.